Sen. Bernie Sanders (I-Vt.) will unveil a plan Thursday to ban privately run jails and prisons, which he says have a “perverse incentive” to increase the number of incarcerated people in the country.

Under the proposal by the Democratic presidential hopeful, the federal government would have three years to end its practice of using private companies to keep people behind bars. The ban would also apply to state and local governments, which have increasingly turned to private contractors in a bid to save money.

“It runs counter to the best interests of our country,” Sanders said in an interview Wednesday. “You should not be making a profit off of putting people in prison.”

Sanders’s “Justice Is Not For Sale Act,” which he plans to introduce as legislation in Congress, also includes several provisions intended to dramatically reduce the number of immigrants who are held in detention facilities while awaiting court hearings on their legal status.

Good. This blog is all for privatisation of state-owned industries and competitive free markets, but there is a limit to how far small government absolutism should go.

The most sacred and fundamental powers of any democratic government are the power to wage war and the power to imprison (or in America’s case, even execute) a citizen found guilty of committing a crime. Both matters are far too serious to be left to the private sector, especially for so tawdry a reason as cost reduction.

Just as Western democracies now rely on volunteer armies for defence and (generally – again, with some regrettable exceptions) eschew using paid mercenaries to do their dirty work, so the state, at whatever level of government is best applicable, should be directly responsible for the welfare and rehabilitation of offenders. Contracting the job out to private firms, ostensibly in order to save taxpayer money, is wrong and often counterproductive, producing the kind of perverse incentives correctly identified by Bernie Sanders. Besides which, the idea of private companies incarcerating citizens under government contract is morally repugnant, whether it is done in Britain, America or elsewhere.

There are plenty of things ripe for privatisation in America, including Amtrak (a giant taxpayer subsidy for wealthy elites living in the Acela corridor) and the United States Postal Service. In this day and age, there is less and less argument for the government having an active hand in transporting people, goods or items of correspondence. So by all means, let’s privatise what government has no business doing in the first place.

But when it comes to the most essential functions of government, some things ought never to have been handed over to the private sector in the first place. And the awesome power and responsibility which comes with incarcerating one’s fellow citizens is a case in point.